Contents
What is 0x9e3779b9?
0x9e3779b9 is the integral part of the Golden Ratio’s fractional part 0.61803398875… (sqrt(5)-1)/2, multiplied by 2^32. Hence, if φ = (sqrt(5)+1)/2 = 1.61803398875 is the Golden Ratio, the hash function calculates the fractional part of n * φ, which has nice scattering properties.
What is Fibonacci hashing?
The Fibonacci hashing method is essentially the multiplication hashing method in which the constant a is chosen as the integer that is relatively prime to W which is closest to. . The following table gives suitable values of a for various word sizes.
Which property makes a hash valid?
A good hash function satisfies two basic properties: 1) it should be very fast to compute; 2) it should minimize duplication of output values (collisions).
What are the different hashing methods?
There are many different types of hash algorithms such as RipeMD, Tiger, xxhash and more, but the most common type of hashing used for file integrity checks are MD5, SHA-2 and CRC32. MD5 – An MD5 hash function encodes a string of information and encodes it into a 128-bit fingerprint.
Why is TEA not a Feistel cipher?
TEA is an iterated block cipher that encrypts 64 bit blocks using a 128 bit key. It uses a relatively weak nonlinear mixing function over many rounds. There are no precomputed tables, key schedules, etc. TEA is not a Feistel cipher.
Is TEA a Feistel cipher?
TEA operates on two 32-bit unsigned integers (could be derived from a 64-bit data block) and uses a 128-bit key. It has a Feistel structure with a suggested 64 rounds, typically implemented in pairs termed cycles. As a result, TEA is especially bad as a cryptographic hash function.
Where do ” magic ” hashings like 0x9e377b9 come from?
Use a hash function that is quick to calculate (such as the hash function you found, or Murmurhash3_32), and make each hash bucket into the root of a balanced binary search tree. So, an ordinary separately chained hash table has each bucket as a linked list, which is slow if lots of values hash to the same bucket.
Is it bad to use magic numbers in programming?
Magic numbers are bad, and they should never be used. Constants such as those mentioned should be given proper descriptive variable names, and perhaps even comments should be added to where they are defined. Then, every appearance of the values in the code should be in the form of the named variable.
Which is the best hash function with a secret seed?
Your hash function doesn’t have a secret random seed. Murmurhash3_32 has a secret random seed, but it has seed-independent multicollisions due to the small internal state. The best hash function having near cryptographical security and still nearly acceptable performance is probably SipHash.